This project will examine porliferation, metabolism, and interactions of retinal vascular cells by means of an established tissue culture model. Knowledge of the contributions of each cell type to the functional and structural integrity of the retinal circulation is important for understanding and treating retinal neovascularization in general and diabetic retinopathy in particular. These studies may lead to the discovery of agents capable of regulating retinal vascular cells in vivo. The response of retinal vascular cells to various growth agents and conditioned media will be assayed by means of total cell counts. The roles of cell density, age of cells at time of initial culture, and number of passages at assay will be studied. The metabolic functions of retinal vascular endothelial cells, pericytes, and smooth muscle cells from bovine eyes will be examined by analysis of sorbitol production, angiotensin-covering enzyme activity, and basement membrane and fibronectin synthesis. The construction of an "artificial retinal-vessel wall" in tissue culture will allow evaluation of the "cell feeder" function of retinal pericytes and smooth muscle cells upon endothelial cell proliferation and synthesis of basement membrane materials. These studies are expected to help elucidate the role of retinal vascular cells in the pathogenesis of diabetic retinopathy.